1. Field of the Invention
The present invention relates to a liquid discharging head for discharging desired liquid by generating a bubble formed by applying thermal energy to the liquid, and more particularly, it relates to a liquid discharging head having a movable member displaced by generating a bubble, a head cartridge having such a liquid discharging head, and a liquid discharging apparatus.
The present invention is applicable to recording apparatuses such as printers for effecting the recording on a recording medium such as a paper sheet, a thread sheet, a fiber sheet, a cloth, a leather sheet, a metal sheet, a plastic sheet, glass, wood, ceramic sheet and the like, copying machines, facsimiles having a communication system, and word processors having a printer portion, and to industrial recording apparatuses combined with various processing devices.
Incidentally, in this specification and claims, a term xe2x80x9crecordingxe2x80x9d means not only application of a significant image such as a character or a figure onto a recording medium but also application of a meaningless image such as a pattern onto a recording medium.
2. Related Background Art
It is already known to provide an ink jet recording method, i.e., so-called bubble jet recording method in which change in state of ink including abrupt change in volume (generation of a bubble) is caused by applying energy such as heat to the ink and the ink is discharged from a discharge port by an acting force based on the change in state to adhere the ink onto a recording medium, thereby forming an image on the recording medium. As disclosed in U.S. Pat. No. 4,723,129, a recording apparatus using such a bubble jet recording method generally includes discharge ports for discharging ink, ink passages communicated with the discharge ports, and electrothermal converters as energy generating means disposed in the liquid passages and adapted to generate energy for discharging the ink.
According to such a recording method, a high quality image can be recorded at a high speed with less noise, and, in a head carrying out this method, since the discharge ports for discharging the ink can be arranged with high density, a recorded image having high resolving power and a color image can easily be obtained by a compact recording apparatus. Thus, recently, the bubble jet recording method has been applied to many office equipments such as printers, copying machines, facsimiles and the like, and is also applied to industrial systems such as print apparatuses.
As the application of the bubble jet technique to various field is increased, the following various requirements have recently been desired.
For example, regarding the requirement of improvement in energy efficiency, a heat generating element has been optimized by adjusting a thickness of a protection film. This method is effective in the point that transfer efficiency of generated heat to liquid is enhanced.
Further, in order to obtain a high quality image, there has been proposed a driving condition for providing a liquid discharging method capable of discharging the ink effectively at high speed due to stable bubble formation, and, in view of high speed recording, there has also been proposed the improvement in a liquid passage design to obtain a liquid discharging head in which liquid corresponding to discharged liquid can be refilled to the liquid passages quickly.
Among various liquid passage designs, a liquid passage structure as shown in FIGS. 44A and 44B is disclosed in the Japanese Patent Application Laid-Open No. 63-199972. The liquid passage structure and a head manufacturing method disclosed in the above Japanese Patent Application Laid-Open No. 63-199972 are inventions based on a back-wave (pressure directing toward a direction opposite to a direction to the discharge port, i.e., pressure directing toward a liquid chamber 12) generated due to bubble generation. The back-wave is known as loss energy, since it is not directed toward the discharge port.
The invention shown in FIGS. 44A and 44B includes valves 10 spaced apart from bubble generating areas of heat generating elements 2 and disposed opposite to discharge ports 11 with respect to the heat generating elements 2.
In FIG. 44B, the valve 10 has an initial position where a leaf of the valve is contacted with a ceiling of a liquid passage 3, and, when the bubble is generated, the leaf of the valve is suspended into the liquid passage 3. In this technique, the energy loss is suppressed by controlling a part of the back-wave by means of the valves 10.
However, with the above-mentioned arrangement, as can be understood from the observation of the case where the bubble is generated in the liquid passage 3 containing the liquid to be discharged, suppression of the part of the back-wave is not practical to the discharging of the liquid.
As mentioned above, the back-wave itself does not relate to the liquid discharging directly. At the time when the back-wave is generated in the liquid passage 3, as shown in FIG. 44A, a part of pressure of the bubble which directly relates to the liquid discharging already establishes a condition that the liquid can be discharged from the liquid passage 3. Accordingly, it is apparent that, even when the part of the back-wave is suppressed, the suppression does not influence upon the liquid discharging greatly.
On the other hand, in the bubble jet recording method, since the heating of the heat generating element contacted with ink is repeated, ink deposit is accumulated on a surface of the heat generating element due to overheat of ink. Depending upon the kind of ink, a large amount of deposit is accumulated on the heat generating element, with the result that the generation of the bubble becomes unstable, thereby causing the poor ink discharging. Further, when the liquid to be discharged is easily deteriorated by heat or when liquid in which an adequate bubble is hard to be formed is used, it has been desired that the liquid to be discharged is not deteriorated and good liquid discharging is achieved.
In view of the above problems, there has been proposed a liquid discharging method wherein liquid (bubble liquid) in which a bubble is formed by heat is different from liquid (discharge liquid) which is to be discharged and the liquid is discharged by transmitting pressure generated by bubble formation to the discharge liquid, as disclosed in the Japanese Patent Application Laid-Open Nos. 61-69467 and 55-81172, and U.S. Pat. No. 4,480,259. In such a method, the discharge liquid (ink) is completely isolated from the bubble liquid by a flexible diaphragm made of silicone rubber and the like to prevent the discharge liquid from directly contacting with the heat generating elements and the pressure generated by the bubble formed in the bubble liquid is transmitted to the discharge liquid by deformation of the flexible diaphragm. With this arrangement, the deposit can be prevented from being accumulated on the heat generating elements and degree of freedom of selection of the discharge liquid can be increased.
However, in the arrangement in which the discharge liquid is completely isolated from the bubble liquid, since the pressure due to the formation of the bubble is transmitted to the discharge liquid by expansion/contraction deformation of the flexible diaphragm, the pressure of the bubble is greatly absorbed by flexible diaphragm. Further, since a deformation amount of the flexible diaphragm is not so great, although the advantage of separation between the discharge liquid and the bubble liquid can be obtained, energy efficiency and/or discharging ability may be worsened.
The present invention premises that fundamental discharging feature of a conventional method for discharging liquid by forming a bubble (particularly, bubble formed by film-boiling) in a liquid passage is improved to the extent that could not be considered by conventional techniques from the point of view which could not be supposed conventionally.
The premise is obtained by first technical analysis based on operation of a movable member in the liquid passage for analyzing the principle of a moving mechanism of the in the liquid passage to provide a new liquid discharging method utilizing a bubble (which could not be obtained in the conventional techniques) and a head used in such a method on the basis of the principle of the liquid discharging, second technical analysis based on the principle of the liquid discharging due to the formation of the bubble, and third analysis based on a bubble forming area of a bubble forming heat generating element.
On the basis of these analyses, by providing a positional relation between a fulcrum of the movable member and a free end of the movable member in such a manner that the free end is positioned near the discharge port, i.e., at a downstream side of the fulcrum, and by arranging the movable member in a confronting relation to the heat generating element or the bubble forming area, a new technique for positively controlling the bubble is obtained.
In this new technique, it is most important that a downstream side growth portion of the bubble is considered in view of energy (which can be applied from the bubble itself to the liquid discharge) in order to improve the discharging feature or ability remarkably. That is to say, the discharging efficiency and discharging speed can greatly be improved by directing the downstream side growth portion of the bubble toward the discharging direction efficiently. The inventors proposed a high technical level (greatly higher than the conventional technical levels) in which the downstream side growth portion of the bubble is positively shifted toward the free end of the movable member. In the high technical level, it was found that it is preferable to consider structural factors of the movable member and the liquid passage associated with the growth of the bubble at a downstream side of the heat generating area for forming the bubble (for example, at a downstream side of a center line passing through a center of area of the electrothermal converter in the liquid flowing direction) or at a downstream side of a center of area of a surface for controlling the bubble formation, and that a refilling speed can greatly be increased by considering the arrangement of the movable member and the structure of the liquid supply passage.
Particularly, the present invention aims to utilize the above-mentioned discharging principle more effectively and provides more stable discharging feature by improving the construction or arrangement of the movable member.
A first object of the present invention is to provide a liquid discharging head which can suppress side loss of bubble pressure caused by displacement of a movable member due to formation of a bubble and improve discharging efficiency and a discharging force more effectively.
A second object of the present invention is to provide a liquid discharging head which enhances orientation of the growth of a bubble and improves discharging efficiency and a discharging force more effectively.
A third object of the present invention is to provide a liquid discharging head which can surely prevent bubble liquid from mixing with discharge liquid and perform good liquid discharging.
In addition, a fourth object of the present invention is to provide new liquid discharging principle by fundamentally controlling a bubble generated.
A fifth object of the present invention is to provide a liquid discharging head which can greatly reduce accumulation of heat in liquid on a heat generating element and reduce pressure of a residual bubble remaining on the heat generating element, thereby achieving good liquid discharging, while improving discharging efficiency and a discharging force.
A sixth object of the present invention is to provide a liquid discharging head which can prevent an inertia force of a back-wave from acting toward a direction opposite to a liquid supplying direction and increase refill frequency by reducing a retard amount of meniscus by utilizing a valve function of a movable member, thereby increasing a recording speed.
A seventh object of the present invention is to provide a liquid discharging head which can reduce deposit on a heat generating element, can widen application range of discharge liquid, and can enhance discharging efficiency and a discharging force.
An eighth object of the present invention is to provide a liquid discharging head which can increase degree of freedom of selection of liquid to be discharged.
A ninth object of the present invention is to provide a liquid discharging head which can be manufactured easily and cheaply by reducing the number of parts constituting liquid introduction passages for supplying a plurality of liquids and can be made compact.
To achieve the above objects, the typical aspects of the present invention are as follow.
Namely, the resistance to the liquid in the flow passage when the movable member is displaced is smaller than the resistance for returning the movable member to the initial position.
Additionally, the movable member has a recessed shape at the side (the second liquid flow passage) faced to the bubble generating area when the movable member is displaced due to the bubble. According to this arrangement, the movable member has a portion for enclosing the bubble at a surface directly receiving the pressure due to the generation of the bubble. More particularly, accoring to the present invention, there is provided a liquid discharging head comprising a discharge port for discharging liquid, a bubble generating area for generating a bubble in the liquid, a movable member disposed in a confronting relation to the bubble generating area and shiftable between a first position and a second position more spaced apart from the bubble generating area than the first position, and side members integrally formed with at least parts of the movable member on its both sides and shiftable together with the movable member and adapted to cover sides of a bubble generated, and wherein the movable member is shifted from the first position to the second position by pressure due to generation of the bubble in the bubble generating area, and the bubble is more expanded downstream than upstream of a direction toward the discharge port by the shifting of the movable member.
Alternatively, the present invention may provide a liquid discharging head comprising a discharge port for discharging liquid, a liquid passage including a heat generating element for generating a bubble in the liquid by applying heat to the liquid and a supply passage for supplying the liquid onto the heat generating element from an upstream side of the heat generating element along the heat generating element, a movable member disposed in a confronting relation to the heat generating element and having a free end near the discharge port and adapted to displace the free end by pressure generated by generation of the bubble, thereby directing the pressure toward the discharge port, and side members integrally formed with at least parts of the movable member on its both sides and shiftable together with the movable member and adapted to cover sides of a bubble generated.
Alternatively, the present invention may provide a liquid discharging head comprising a discharge port for discharging liquid, a heat generating element for generating a bubble in the liquid by applying heat to the liquid, a movable member disposed in a confronting relation to the heat generating element and having a free end near the discharge port and adapted to displace the free end by pressure generated by generation of the bubble, thereby directing the pressure toward the discharge port, and side members shiftable together with the movable member and adapted to cover sides of a bubble generated, and a supply passage for supplying the liquid onto the heat generating element from upstream of a surface of the movable member near the heat generating element.
Alternatively, the present invention may provide a liquid discharging head comprising a first liquid passage communicated with a discharge port, a second liquid passage including a bubble generating area for generating a bubble in the liquid by applying heat to the liquid, a movable member disposed between the first liquid passage and the bubble generating area and having a free end near the discharge port and adapted to displace the free end toward the first liquid passage by pressure generated by generation of the bubble in the bubble generating area, thereby directing the pressure toward the discharge port of the first liquid passage, and side members integrally formed with at least parts of the movable member on its both sides and shiftable together with the movable member and adapted to cover sides of a bubble generated.
Alternatively, the present invention may provide a liquid discharging head comprising a grooved member including a plurality of discharge ports for discharging liquid, a plurality of grooves for forming a plurality of first liquid passages directly communicated with the respective discharge ports, and a recess forming a first liquid chamber for supplying the liquid to the plurality of first liquid passages; an element substrate on which a plurality of heat generating elements for generating a bubble in the liquid by applying heat to the liquid are disposed; and a separation wall disposed between the grooved member and the element substrate and adapted to constitute a part of wall of second liquid passages corresponding to the heat generating elements and having a movable member shiftable toward the first liquid passages by pressure caused by generating a bubble at a position confronting to the heat generating element; and wherein the movable member is provided at least parts of its both sides with side members shifted together with the movable member and adapted to cover both sides of the bubble generated.
Alternatively, the present invention may provide a liquid discharging apparatus for discharging recording liquid by generating a bubble, comprising the above-mentioned liquid discharging head, and a drive signal supplying means for supplying a drive signal for discharging the liquid from the liquid discharging head.
Alternatively, the present invention may provide a liquid discharging head comprising an element substrate on which a plurality of discharge energy generating elements for generating a bubble for discharging liquid are disposed, a plurality of discharge ports provided in correspondence to the plurality of discharge energy generating elements and each directly communicated with a common liquid chamber to which the liquid is supplied, a bubble generating area for generating a bubble in the liquid, and a movable wall disposed in a confronting relation to the bubble generating area and shiftable between a first position and a second position more spaced apart from the bubble generating area than the first position, and wherein the movable wall has a free end downstream of a liquid flowing direction and further wherein the movable wall is shifted from the first position to the second position by pressure caused by generating the bubble in the liquid by means of the discharge energy generating means to direct the pressure toward the discharge port, thereby discharging the liquid from the discharge port.
Alternatively, the present invention may provide a liquid discharging method performed in a liquid discharging head including an element substrate on which a plurality of discharge energy generating elements for generating a bubble for discharging liquid are disposed, and a plurality of discharge ports provided in correspondence to the plurality of discharge energy generating elements and each directly communicated with a common liquid chamber to which the liquid is supplied, comprising the steps of providing a movable wall disposed in a confronting relation to a bubble generating area for generating a bubble in the liquid and shiftable between a first position and a second position more spaced apart from the bubble generating area than the first position, and shifting the movable wall from the first position to the second position by pressure caused by generating the bubble in the liquid by means of the discharge energy generating means to direct the pressure toward the discharge port, thereby discharging the liquid from the discharge port.
Alternatively, the present invention may provide a liquid discharging head comprising a discharge port for discharging liquid, a liquid passage including a heat generating element for generating a bubble in the liquid by applying heat to the liquid and a supply passage for supplying the liquid onto the heat generating element from upstream side of the heat generating element along the heat generating element, and a movable member disposed in a confronting relation to the heat generating element and having a free end near the discharge port and a fulcrum disposed at an upstream side of the free end and including a recess having a width smaller than a maximum diameter of the discharge port at at least free end of the movable member confronting to the heat generating element and adapted to shift the free end by generation of the bubble to direct pressure caused by the generation of the bubble toward the discharge port.
Alternatively, the present invention may provide a liquid discharging head comprising a discharge port for discharging liquid, a heat generating element for generating a bubble in the liquid by applying heat to the liquid, a movable member disposed in a confronting relation to the heat generating element and having a free end near the discharge port and a fulcrum disposed upstream of the free end and including a recess having a width smaller than a maximum diameter of the discharge port at at least free end of the movable member confronting to the heat generating element and adapted to shift the free end by generation of the bubble to direct pressure caused by the generation of the bubble toward the discharge port, and a supply passage for supplying the liquid onto the heat generating element from upstream of the movable member along a surface of the movable member near the heat generating element.
Alternatively, the present invention may provide a liquid discharging head comprising a discharge port for discharging liquid, a first liquid passage communicated with the discharge port, a second liquid passage including a bubble generating area for generating a bubble in the liquid by applying heat tot he liquid, and a movable member disposed in a confronting relation to the bubble generating area between the first liquid passage and the bubble generating area and having a free end near the discharge port and a fulcrum disposed at an upstream side of the free end and including a recess having a width smaller than a maximum diameter of the discharge port at at least free end of the movable member confronting to the heat generating element and adapted to shift the free end toward the first liquid passage by generation of the bubble to direct pressure caused by the generation of the bubble toward the discharge port of the first liquid passage.
Alternatively, the present invention may provide a liquid discharging head comprising a grooved member including a plurality of discharge ports for discharging liquid, a plurality of grooves for forming a plurality of first liquid passages directly communicated with the respective discharge ports, and a recess forming a first liquid chamber for supplying the liquid to the plurality of first liquid passages; an element substrate on which a plurality of heat generating elements for generating a bubble in the liquid by applying heat to the liquid are disposed; and a movable member disposed in a confronting relation to the element substrate between the grooved member and the element substrate and adapted to constitute a part of wall of second liquid passages corresponding to the heat generation elements and having a free end near the discharge port and a fulcrum disposed upstream of the free end and including a recess having a width smaller than a maximum diameter of the discharge port at at least free end of the movable member confronting to the heat generating element and adapted to shift the free end toward the first liquid passage by generation of the bubble to direct pressure caused by the generation of the bubble toward the discharge port of the first liquid passage.
Alternatively, the present invention may provide a head cartridge comprising the above-mentioned liquid discharging head and a liquid container for holding the liquid supplied to the liquid discharging head.
Alternatively, the present invention may provide a liquid discharging apparatus comprising the above-mentioned liquid discharging head, and a drive signal supplying means for supplying a drive signal for discharging the liquid from the liquid discharging head.
Alternatively, the present invention may provide a liquid discharging head comprising a discharge port for discharging liquid, a liquid passage communicated with the discharge port, a bubble generating area for generating a bubble in the liquid in the liquid passage, and a movable member disposed in a confronting relation to the bubble generating area in the liquid passage and adapted to be shifted by pressure caused by generating the bubble at the bubble generating area to direct the pressure toward the discharge port and to be returned to its initial position by negative pressure due to contraction of the bubble, and wherein resistance of the movable member against the liquid in the liquid passage when it is shifted is smaller than that when it is returned.
Alternatively, the present invention may provide a liquid discharging head comprising a discharge port for discharging liquid, a first liquid passage communicated with the discharge port, a second liquid passage including a bubble generating area for generating a bubble in the liquid by applying heat, and a movable member disposed between the first liquid passage and the bubble generating area and adapted to be shifted toward the first liquid passage by pressure caused by generating the bubble at the bubble generating area to direct the pressure toward the discharge port and to be returned to its initial position by negative pressure due to contraction of the bubble, and wherein resistance of the movable member against the liquid in the first liquid passage when it is shifted is smaller than that when it is returned.
Alternatively, the present invention may provide a liquid discharging head comprising grooved member including a plurality of discharge port for discharging liquid, a plurality of grooves for forming a plurality of first liquid passages directly communicated with the respective discharge ports, and a recess forming a first liquid chamber for supplying the liquid to the plurality of first liquid passages; an element substrate on which a plurality of heat generating elements for generating a bubble in the liquid by applying heat to the liquid are disposed; and a movable member disposed between the grooved member and the element substrate and adapted to constitute a part of wall of second liquid passages corresponding to the heat generating elements and adapted to be shifted toward the first liquid passage by pressure caused by generating the bubble at the heat generating element to direct the pressure toward the discharge port and to be returned to its initial position by negative pressure due to contraction of the bubble, and wherein resistance of the movable member against the liquid in the first liquid passage when it is shifted is smaller than that when it is returned.
Alternatively, the present invention may provide a head cartridge comprising the above-mentioned liquid discharging head, and a liquid container for containing the liquid to be supplied to the liquid discharging head.
Alternatively, the present invention may provide a liquid discharging apparatus comprising the above-mentioned liquid discharging head, and a drive signal supplying means for supplying a drive signal for discharging the liquid from the liquid discharging head.
Alternatively, the present invention may provide a liquid discharging apparatus comprising them above-mentioned liquid discharging head, and a recording medium conveying means for conveying a recording medium onto which the liquid discharged from the liquid discharging head is to be adhered.
As mentioned above, according to the liquid discharging head of the present invention based on the new discharging principle, since the sides of the generated bubble are covered by the side members, the pressure directing to the directions transverse to the liquid flowing direction is also directed toward the liquid flowing direction. And, the bubble growing direction itself is also oriented toward the downstream side, with the result that the growth of the downstream bubble portion becomes greater than the growth of the upstream bubble portion. Consequently, since the liquid near the discharge port can efficiently be discharged toward the discharge port, the discharging efficiency can be improved in comparison with the conventional techniques. For example, in a most preferable embodiment of the present invention, the discharging efficiency could be improved by twice or more in comparison with the conventional techniques.
Particularly, when the movable member has a flexible diaphragm including expansion/contraction portions constituting both sides of the movable member and the expansion/contraction portions are utilized as the side members, the displaced amount of the movable member is regulated by the expansion/contraction portions. As a result, since the degree of opening of the liquid passage near the discharge port caused by the displacement of the movable member becomes constant and bubble pressure acting toward the discharge port also becomes constant, the stable discharging can be achieved.
According to the characteristic arrangement of the present invention, even if the head is placed under a low temperature condition and/or a low humidity condition for a long time. The poor discharging can be prevented. If the poor discharging occurs, merely by effecting a recovery treatment such as preliminary discharge and/or suction recovery, the normal condition can easily be restored.
Specifically, even under a long term placement condition wherein many conventional bubble jet heads having 64 discharge ports occur the poor discharging, in the head of the present invention, only about a half or less of the discharge ports cause the poor discharging. Further, when such head is restored by the preliminary discharge, it was found that, in the conventional head, about 1000 preliminary discharges must be effected for each discharge port; whereas, in the head of the present invention, the head can be restored merely by about 100 preliminary discharges. This means that the recovery time and the liquid loss during the recovery operation can be reduced and the running cost can be reduced greatly.
Further, according to the arrangement of the present invention in which the refilling feature is improved, the response in the continuous liquid discharging, stable growth of the bubble and stability of liquid droplets can be improved, thereby permitting high speed recording due to high speed liquid discharging and high quality image recording.
The other advantages of the present invention will be apparent from the detailed explanation of respective embodiments of the present invention.
Incidentally, in the specification and claims, the terms xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d are referred to regarding the liquid flowing direction from the liquid supply source through the bubble generating area (or movable member) to the discharge port, or the constructional direction.
Further, the term xe2x80x9cdownstream sidexe2x80x9d regarding the bubble itself mainly means a discharge port side portion of the bubble directly relating the liquid discharging. More particularly, it means a bubble portion generated at a downstream of a center of the bubble in the liquid flowing direction or the constructural direction or at downstream of a center of the area of the heat generating element.
Further, in the specification and claims, the term xe2x80x9csubstantially closedxe2x80x9d or xe2x80x9csubstantially sealedxe2x80x9d means a condition that, when the bubble is growing, before the movable member is shifted, the bubble cannot escape through a gap (slit) at a downstream side of the movable member.
In addition, the term xe2x80x9cseparation wallxe2x80x9d means a wall (which may include the movable member) disposed to separate the bubble generating area from an area directly communicated with the discharge port in a broader sense, and means a wall for distinguishing the liquid passage including the bubble generating area from the liquid passage directly communicated with the discharge port and for preventing the mixing of the liquid in both liquid passages in a narrower sense.